6 Needs for rumen motility
1. Inoculate ingest with bacteria and protozoa
2. Mix saliva and ingesta to buffer acids produced by VFAs
3. Elimination of gas produced by bacteria
4. Prevent local accumulation of VFA at site of production
5. Assist VFA absorption through rumen wall
6. Prevent impaction by moving small particles into the lower GIT (omasum, abomasum and beyond)
Does the rumen have an intrinsic pacemaker?
If the rumen does not have intrinsic pacemaker, how does it have motility?
Innervated by Vagal Nerve
- multiple branches innervate different regions
Which contraction is the vagal nerve responsible for in the rumen?
primary and secondary
What does the vagal nerve affect in the motility of the rumen?
Duration of motility
What does the vagal nerve fire based upon?
Activity in the bilateral gastric centers of the medulla
What type of autonomic response does the vagal nerve transmit to the rumen?
Other than the vagal nerve innervation, what is another innervation of the rumen?
Splanchnic motor nerves - sympathetic
- inhibit motility
3 Stimulatory inputs to gastric centres
1. Buccal mechanoreceptors (eating & chewing)
2. Tension receptors (high & low)
3. Epithelial (mucosal) receptors
Affects of tension receptors
Low tension receptors - increase motility
High tension receptors - stop motility
5 inhibitory inputs to gastric centers
1. High threshold tension receptors in reticulum and rumen
2. Tension receptors in abomasum
3. Epithelial receptors in rumen (pH)
5. Drugs (alpha-2 agonsits)
What do tension receptors in rumen cause?
Both increase and decrease rumen motility
2 type of epithelial Receptors
What will acid in abomasum do?
Causes stimulatory signals to increase rumen motility
Explain the primary cycle of rumen motility
Major mixing contraction of ruminoreticulum
Last about 20 secs
Series of events
- Double contraction of reticulum
- Contraction of dorsal rumen sac (cranial to caudal)
- Contraction of ventral rumen sac (crainal to caudal and then caudal to cranial)
Occurs approx once/min
What does frequency of primary cycle depend upon?
Eating: 35-45 secs
Ruminating: 45-60 secs
How do we measure rumen motility through the fistula?
3 Catheters (attached to pressure transducer)
- One into the reticulum
- One under the mat in the dorsal sac
- One in the ventral sac
Connect to polygraph to measure pressure changes